(a) Field of the Invention
This invention relates to compositions from which phenol-formaldehyde resin foams may be prepared. More particularly, it relates to a two-part pack which contains, divided between the two parts of the pack, the materials required to produce a phenol-formaldehyde resin foam. Each part of the pack is stable and shelf-storable.
The major use of this foam system is an insulating material in building construction due to its low flammability and good insulation properties.
(b) Description of the Prior Art
Most foam systems, of which polyurethanes are perhaps the best known are obtained by cross linking a polymer by means of a catalyst, in the presence of a blowing agent. It is the blowing agent which forms the gas which causes the system to foam. This gas can be generated in several ways. It can be obtained chemically, but the most used method, perhaps because it is inherently the simplest, is to incorporate into the foam system a low boiling compound which is liquid under normal storage conditions for the foam components, which does not interfere with the cross linking reaction, but which vapourizes under the influence of the heat generated in that cross linking reaction. It is also necessary that the foaming agent be dispersible, preferably soluble, in one of the components used to make the foam. The commonly used blowing agents are low boiling hydrocarbons such as butane and pentane, or chlorofluorohydrocarbons, such as dichlorodifluoromethane.
Thus, it is apparent that the basic needs which must be met to get a good foam are proper cross linkable resin, a catalyst capable of cross linking that resin, and a blowing agent. It is also apparent that to prepare foam, one simply has to mix together these three reagents, together with any desired surfactants, inert dyes, fillers, plasticizers and so forth.
From the point of view of the user of foam compositions, it is desirable that the foam be obtained with the minimum of effort and without the use of complex or delicate machinery. In some cases, it is known to package the complete foam formulation in a single container, a foam being obtained when the contents are released or expelled from the container. Two examples of foams packaged in a single container are some shaving cream and fire extinguishing formulations. But for the majority of foam formulations it is not possible to place all the components in one container, for the simple reason that the cross linking reaction will rapidly ensue, leading to explosive rupture of the container.
In practice, therefore, the simplest foam formulations call for the mixing of two components, frequently in approximately equal quantities. The equipment needed to do this is well known, having been developed to handle the well known polyurethane foam formulations which call for the admixing of just two components.
Many attempts have been made to provide phenol-formaldehyde foam formulations.
In U.S. Pat. No. 2,629,698, (issued Feb. 24, 1953) R. F. Sterling describes a phenol-formaldehyde resin formulation which will generate a foam when heated. The foaming agent used is a peroxide. As a temperature of between 110.degree. C. and 350.degree. C. is required for this procedure, its commercial applicability is quite limited.
In U.S. Pat. No. 2,653,139, (issued Sept. 22, 1953) R. F. Sterling describes an in-situ foamable phenol-formaldehyde resin formulation. But this formulation requires the continuous mixing of at least three components, in sharply differing amounts. The apparatus required is therefore complex, requiring at least three metering and control valves.
In U.S. Pat. No. 3,298,973 (issued Jan. 17, 1967) Richard W. Quarles et al a flame-resistant and non-punking phenol-formaldehyde resin foam formulation. These foams are again prepared from a plurality of components, and the formulation is placed as soon as it is mixed. These formulations contain a minimum of four independently added components.
In U.S. Pat. No. 3,389,094 (issued June 18, 1968) William J. D'Alessandro describes a phenol-formaldehyde resin foam formulation using a polyhalogenated fluorocarbon, such as trichlorofluoromethane or trichlorotrifluoroethane, as the foaming agent. However, these formulations generally require heating to initiate the foaming reaction, and call for the simultaneous mixing of at least 4 components.
In U.S. Pat. No. 3,484,391 (issued Dec. 16, 1969) S. J. Wheatley et al describe a shock, or impact, and heat resistant phenolformaldehyde foam formulation including fiber glass. These formulations again call for mixing sequentially together, immediately before placement, of at least 4 components.
In U.S. Pat. No. 3,740,358 (issued June 19, 1973) Howard W. Christie et al describe a phenol-formaldehyde resin foam formulation similar to that described by Quarles et al. These formulations are even more complex, calling for a minimum of six components, with no recommendations for any premixing, and also require heating, typically to a temperature of from 140.degree. F. to 180.degree. F. for proper foam formation.
In U.S. Pat. No. 3,870,661 (issued Mar. 11, 1975) Peter J. Crook et al describe what may be termed a self catalysing phenol-formaldehyde resin foam formulation wherein the strong acid moiety required as the cross linking catalyst is directly incorporated into the resin as a pendant sulphonyl group. These formulations again require the mixing simultaneously of at least 4 components to provide a foam.
In U.S. Pat. No. 3,907,723 (issued Sept. 23, 1975) Monique Pretot describes a phenol-formaldehyde foam including resorcinol as a reagent to combat foam acidity. These formulations require the simultaneous or sequential mixing of at least 6 components to provide a foam.
In U.S. Pat. No. 3,915,905 (issued Oct. 28, 1975) Daniel Hanton describes non-burning and self-extinguishing phenol-formaldehyde resin foam formulations, utilizing a nitrogenous compound to impart the thermal characteristics. These formulations call for mixing at least four components simultaneously, and also require heating to an unspecified temperature for proper foam formation.
In U.S. Pat. No. 3,953,645 (issued Apr. 27, 1976) E. K. Moss describes phenol-formaldehyde resin foam formulations involving particular phenol-formaldehyde resins. These formulations require the simultaneous mixing of at least five components, the only premixing described being addressed to the formulation of multi-component acid catalysts.
In U.S. Pat. No. 4,122,045 (issued Oct. 24, 1978) William L. Garrett et al described a non-corrosive phenol-formaldehyde resin foam formulation. These formulations require the simultaneous mixing of at least five components, of which only some can be pre-mixed: even so, the minimum number of components appears to be four.
Through all of this prior art there runs two common threads. In none of these references is there described a formulation which pre-mixes the components required to make a phenol-formaldehyde resin foam in such a way that the final foaming step requires the admixture of only two components. Also, in none of these references is there described a formulation which permits the final foaming step to be divorced in both place and time from the described mixing steps. All of these references describe procedures in which the formulation is taken immediately right through to a placed foam.